A conventional speaker is basically provided with a function for outputting sound or high and low sound levels depending on a user's preference. In a Karaoke room equipped with an accompaniment machine, a user sings a song along with the accompaniment outputted through a speaker, while watching a monitor screen, which displays a background image along with lyrics.
However, in the conventional art, since a monitor and a speaker are separately installed in a limited and narrow space, the user may feel inconvenience owing to the limited and narrow space. In addition, since a background image displayed on a monitor may not be synchronized with the sound outputted from the speaker, the user may feel bored. The speaker installed at a huge event concert is expensive and installed at multiple places, so that the monitors or screens showing images may be overlapped with the speakers. It is not easy to properly install multiple speakers and monitors in the limited spaces, so that it is impossible to maximize the event effects.